Orthopedic Board Prep: Comprehensive Interactive Rheumatoid Foot Exam
Key Takeaway
Active synovitis in a rheumatoid foot is reliably indicated by warmth and erythema over the metatarsophalangeal joints, signifying acute inflammation. In contrast, fixed hallux valgus, bunionette deformity, callosities, and MTP joint subluxation represent chronic disease consequences or fixed deformities, not necessarily ongoing active inflammation. Palpation for swelling and tenderness further confirms synovitis.
I am presenting a patient with a chronic history of rheumatoid arthritis. Look at this radiograph of the forefoot. Describe the findings and explain the mechanical consequences of this pattern of deformity.
Candidate: The radiograph shows severe hallux valgus with interphalangeal joint involvement. The lesser toes show MTP joint subluxation, widening of the intermetatarsal angles, and what appears to be plantar plate insufficiency. The patient likely has pain under the metatarsal heads.
Failing to mention the "cock-up" deformity or the proximal migration of the plantar fat pad (as suggested by the MTP joint dislocation). Candidates often focus only on the hallux valgus while ignoring the global forefoot instability, which is the primary source of symptoms in rheumatoid disease.
Structure your answer systematically: 1. Radiographic Findings: Note the severe hallux valgus, the lateral deviation of the lesser toes, and the complete dorsal subluxation/dislocation of the lesser MTP joints. 2. Pathophysiology: Explain the destruction of the plantar plate and collateral ligaments, leading to the loss of the plantar metatarsal fat pad cushioning. 3. Clinical Correlation: State that this directly results in symptomatic "transfer metatarsalgia," where weight is concentrated on the exposed metatarsal heads, leading to painful callosities and the "paper test" positivity. Mention the risk of secondary skin ulceration due to the prominence of the metatarsal heads.
Following up on this patient, they are now complaining of significant difficulty with gait and frequent tripping. How do you assess the stability of these MTP joints, and what are the implications for your surgical plan?
Candidate: I would perform a drawer test on the lesser MTP joints to check for plantar plate rupture. If it's unstable, I'd consider a metatarsal head resection or an MTP joint arthroplasty, and maybe a fusion of the hallux MTP joint.
Proposing surgery without assessing the hindfoot. In RA, the forefoot is often just one part of a collapsing structure; if you correct the forefoot but leave a rigid hindfoot valgus, your forefoot surgery will fail due to ongoing abnormal loading.
1. Clinical Assessment: Describe the MTP Drawer test to assess sagittal plane instability (plantar plate). 2. Structural Assessment: Emphasize the need to check the flexibility of the hindfoot (Single heel-rise test) and the status of the Achilles tendon (Silfverskiöld test). 3. Surgical Strategy: Discuss a staged approach or combined correction. For the forefoot: metatarsal head resections (e.g., Clayton or Hoffmann procedure) versus joint-preserving fusions, depending on the bone quality and degree of deformity. Crucially, mention that if there is fixed hindfoot valgus, it must be addressed (e.g., calcaneal osteotomy or arthrodesis) to ensure the forefoot correction lasts.
